1. Field of the Invention
The present invention relates to computed tomographic (CT) imaging, and in particular to CT imaging using scanograms to estimate line data from circular scans.
2. Discussion of the Background
In three-dimensional (3D) cone-beam computed tomography, the circular scan is widely used because of its convenience. It is well known that the projection data acquired from a cone-beam circular scan are not sufficient for volumetric reconstruction. The so-called cone-beam artifacts are found in the reconstructed images from circle-only cone-beam scan data. The low frequency shadow artifacts can be reduced by interpolation in the radon space. The high frequency artifacts due to the longitudinal abrupt change in the imaged subject are difficult to handle. A typical high frequency cone-beam artifact is the streaks off spines.
To eliminate the cone beam artifacts in circular cone-beam scans, an additional line scan, arc scan, or helical scan is usually performed to make the data complete for the volumetric reconstruction. The additional scan may increase the complexity of the scan protocol and increase the scan time and radiation dose.